The following is not an admission that anything described below is prior art or common general knowledge.
In wastewater treatment plants, one of the available unit processes may involve treatment of the wastewater with anaerobic microorganisms. Even though an anaerobic process tank may be open, in the absence of added oxygen, the prevailing conditions in the water in the tank may be anaerobic. Anaerobic microorganisms populate the tank and convert biologically degradable material in the wastewater primarily into water and biogas, which is primarily carbon dioxide and methane.
In membrane bioreactors, solid-liquid separation of the degrading or degraded wastewater is performed through a membrane filter. The membrane filter may be immersed directly into a process tank, or may be immersed in a separate tank with an inlet from a process tank and an outlet back to the same or another process tank. The membranes are typically in the microfiltration or ultrafiltration range. A flux of permeate (filtered water) may be drawn through the membranes by suction applied to an inside volume of the membrane filter.